Device for determining pressure in gun bores



. Aug. 27, 1940.

J. w. MOSEMAN 2,212,547

DEVICE FOR DETERMINING PRESSURE IN GUN BORES Filed Aug. 1'7, 1959 lT'LvETLL EH" JEN-L11 WilLiumMnsamun Attcn neys Patented Au. 7,, 1'

a rnnssunn in John William Moseman. Bethesda, Md. u plication August 17, 1939, Serial No. 290,638

11 Claim.

The invention described herein may be manufactured and used by or for the Government for governmental purposes, without the payment to me of any royalty thereon.

6 This invention relates to a pressure gage of the copper crusher type.

In the design of guns today and more particularly in the design of intermediate and subcaliber cannon, it is usual to first select the.

ammunition to be used and then'desig'n the cannon around the selected ammunition. In following this procedure the caliber of the gun is determined, the weight of the projectile to be used I with the gun selected and the weight of the powder charge necessary to give the selected projectile the required muzzle velocity calculated. However, inasmuch as the calculated gas pressures of a given lot of powder will not always be in accordance with the actual service pressure developed it may be necessary to use a greater or less amount of powder than that calculated. is used it is tioning of the ammunition casein respect to its obturatlon in the designed chamber of the gun before further design of the gun.

It is proposed by this invention to provide an expeditious andeconomical means of accurately determining the actual service pressures developed to give the required muzzle velocity along with a satisfactory test of the selected ammunition with respect to the design of the tube to be employed in the gun without the necessity of designing and building a complete gun. by mere- 1y designing and constructing a gun tube for theproposed gun that may be inserted within the bore and be fired by the firing mechanism of some existing gun adapted for the purpose. In this manner the true service pressures developed in to obtaining the required muzzle velocity and muzzle energy may be actually determined before the design of the remainder of the gun to give the designer information vital to the adequate design of cannon.

To render feasible the execution of the design of a gun in accordance with. this invention it is essential that an accurate and expeditious deter- I mination of the breech pressures necessary for the required muzzle velocity be made available and it is therefore an object of this invention to provide a copper crusher gage particularly adapted for use in determining the pressure developed in the bore of a sub-caliber tube.

It is a further object of the invention to pro vide a copper crusher gage for use with a gun Moreover, where fixed ammunition very desirable to check the i'uncof the tube and (Gil. 261-=-1) (Granted under the act at amended April 30, 11928;

March 3, 1883, as 3% ill. G. 757) barrel that may be inserted in a radially bored external recess of the barrel whereby the gage may be functionally secured'to the barrel within the outside periphery thereof to eliminate the formation of any obstructions on the peripheral iii surfaceof the barrel.

It is a. still iiuther object of the invention to provide an external copper crusher gage that may be secured to a gun barrel in such manner as to efiectively measure the bore pressure with-' 31% out having any portion protruding within the bore whereby fixed ammunition may be chambered in the bore and the density of loading of the powder charge of separate loading component ammunition will not be varied from the m density of loading of the powder charges used in service so that pressures comparable to pressures developed under service conditions may be measured. I

The specific nature of the invention as well as 3% other objects and advantages thereof will clearly appear from a description of a preferred embodiment as shown in the accompanying drawing in which:

Fig. 1 is a sectional view showing the gage of 955 this invention applied on a sub-caliber tube inserted in the bore of a. major caliber gun.

Fig. 2 is a top plan view of the gage.

Referring now to the drawing by characters of reference and more is shown at In the tube of a major caliber gun having a sub-caliber tube H inserted therein in its normal firing position.

The tube H shown is primarily for use with fixed ammunition, but obviously may be used 3 with ammunition loaded by separate components. As indicated at H the tube H is radially bored externally to form a generally cylindrical recess extending inward from the outer peripheral surface of the tube. bottom of recess 92 is counterbored axially of the recess on a decreased diameter to provide a planar annular shoulder I 3 for a purpose made apparent hereinafter and communication between the bore surface defining the bottom of recess l2 adjacent the port M is counterbored to form a second planar annular shoulder or abutment l5 and the surface defining the side walls of the recess are iii?) threaded as indicated by the numeral IS.

The pressure gage generally indicated by the numeral H comprises a cylindrical housing member l5 externally threaded as at it to be threaded into the recess II in inter particularly to Fig, 1 there W- The surface defining the 40'.

recess is established by a cylindrical port H arranged axially of the recess." The threaded engagement with the threads it. At its no lower end the cylindrical housing member is axially bored to provide a recess 29 having its side walls threaded as at 2i and its bottom defining surface terminating in a plane normal to the aids of the housing member. An axial counterbore 22 of smaller diameter than the recess is provided in the bottom of the recess to provide an annular abutment 23 and plane anvil seat or surface 24 axially displaced relative to abutment Z3 and lying in a plane normal to the axis of the housing. At its normally upper end the housing member is of arcuate shape in cross section and is provided with a plurality of drill holes or similar bores 25 disposed in axially parallel relation with the axis of the housing member and adapted to cooperate with a similar number of pins of a wrench, not shown, for threading the housing member into the recess l2.

A cylindrical plug 26 externally threaded at 21 and adapted to be secured in the recess 2d of the housing member in interthreaded engagement is provided with a plane end surface 28 engageable with the abutment 23 in sealed relation. The plug is of such axial extent as to project from without the recess of the housing member and is provided with a cylindrical axial bore 29 outwardly flared on a small radius where it joins the end surface 29 of the plug.

A piston having an enlarged circular head 3| adapted to snugly fit within the counterbore 22 of the housing member and provided with a plane surface 32 adapted to confront the anvil surface 24 in parallel relation is made integral with or otherwise suitably secured to a cylindri cal piston stem 33 ground and lapped to substantially perfectly fit the bore 29. The piston head and stem are joined by an upwardly flaring surface 34 of substantially the same configuration as the flared surface joining the bore 29 to the end surface 28 of the plug. When the piston is assembled in the plug the piston stem will terminate a short distance above the lower end of the bore to provide a predetermined void in prolongation of the bore l4 and obturation is accomplished by means of an inverted cup-shaped gas check 35 made of copper or similar material inserted in the end of the bore 29 and pressed home in contact with the adjacent end of piston stem by a suitable tool.

plug is threaded into recess 20 with its surface 2| engaging abutment 23 is then positioned in bore 22 with one of its ends seated on anvil surface 24 in bearing relation. If desired auxiliary means such as a rubber ring may be used to initially hold the copper pressurecylinder in the bore 22 by inserting the ring over the pressure cyllnderintermediate its ends and then compressing the ring between the pressure cylinder and adjacent walls of the bore to frictionally hold the pressure cylinder within the'bore in properly seated relation. The plug .26 with its assembled piston is then threaded into the recess 26 until the piston surface 32 firmly engages the adjacent end of the copper pressure cylinder and surface 28 abuts abutment 23 in sealed relation. A suitable gasket 31 of copper or similar material is inserted in the recess i2 on shoulder l5 and the assembled gage is then threaded in the recess until the gasket 37 is tightly compressed between the end of the plug 25 and shoulder l5. Preferably the plug 26 is provided with an annular projection 38 adapted to fit in a cooperating small counterbore 39 near the upper end of the port it to protect the gasket 31 from the full force of the hot gases of explosion. The gage is now assembled in the recess it with the piston stern aligned with port l4 and conditioned for operation. The sub-caliber tube It with its assembled gage is now inserted in the bore of a gun tube such as id and a round of fixed ammunition 4% chambered in the tube ii. The breech closure is locked and the chambered round of ammunition td fired whereupon the pressure of the gases of explosion will perforate the case of the round of ammunition underlying port i4 and urge the piston stem upwardly to compress the pressure cylinder 36. After firing the round of ammunition the gage is disassembled and the set of the pressure cylinder measured by means of a micrometer caliper. The set of the cylinder measured may then be used as an argument to enter a table of pressures that have been previously prepared to determine the pressure developed for any particular round fired.

Having now particularly described what is at present considered a preferred embodiment of the invention what I claim as new and desire to secure by Letters Patent is:

In a device for determining the pressure developed in the bore of a gun by means of a crusher block wherein the wall of the bore is provided with a cylindrical internal threaded radial recess, said recess being coaxially counterbored with a gasket in the bottom of the counterbore and a coaxial passage of less cross-sectional area than the counterbore placing the recess in communication with the interior of the bore, of an externally threaded cylindrical housing member, said member being formed at one end to provide an internally threaded axially disposed recess terminating in a plane normal to its axis and axially counterbored on a substantially smaller diameter to provide an annular shoulder in said plane and an axially disposed anvil surface normal to its axis, an externally threaded cylindrical plug having a plane end surface threaded in the recess of the housing member with its plane end surface in sealed relation with said annular shoulder, said plug being axially bored and having an annular projection surrounding the lower end of its bore, a piston disposed in the counterbore of the housing member having a plane bearing surface parallel to the anvil surface and a piston stem secured to the piston and reciprocally mounted in the bore of the plug, whereby said housing may be threaded into and completely housed in the radial recess in the wall of the gun bore with the outer end of the plug engaging said gasket in sealed relation, the piston stem exposed to the interior of the gun bore and said'annular projection extending into and snugly fitting the passage to protect the gasket from direct action of gases.

JOHN WILLIAM MOSEMAN. 

